The prior art systems for the remote locating of the repeaters may be distinguished by two types, a first type in which a unique address is assigned to each repeater, and a second type in which such an address is not used.
A system of the first type is described in German Patent Specification No. 22 15 836 issued June 28, 1973. In this known system the address consists of a unique frequency assigned to each repeater. This frequency is obtained in the tele-location transmitter by a suitable choice of the signals for the on-off modulation of the carrier signals. Recognition of the said frequency in a repeater then accomplishes looping of the forward and return paths. One disadvantage of this type of system is the use of filters for the frequency detection, as filters are usually bulky circuits having a delicate tuning. A second disadvantage also results from the use of filters and resides in the fact that said filters must be tuned in a manner which is different for every repeater, which seriously hampers the installation of the repeaters.
A system of the second type is disclosed in German "Auslegeschrift" No. 26 53 201 issued Aug. 31, 1978. In essence, said prior art system employs two kinds of signals: the signals of the first type are preparatory signals which are transmitted to make the regenerators included in the repeaters suitable for receiving the signals of the second type, which form loop commands. One disadvantage of this system resides in the fact that two kinds of signals must be generated and recognized in each individual repeater. A second disadvantage is that each repeater must be provided with a separate transmitter for retransmitting the preparatory signals to the following repeater.
It is an object of the invention to provide a tele-locating system defined in the preamble which belongs to the said second type of system but does not have the disadvantages mentioned above.